The present invention relates to certain novel 3,3,3-trifluoropropyl derivatives of naphthalene, 1-methylnaphthalene or 2-methylnaphthalene, and to a novel process for preparing the derivatives.
As a means for synthesizing an aromatic compounds having benzene ring substituted by 3,3,3-trifluoropropyl group, only one process has been proposed (U.S. Pat. No. 3,080,428), in which 3,3,3-trifluoropropyl ether, (CF.sub.3 CH.sub.2 CH.sub.2).sub.2 O, is brought into reaction with benzene in the presence of hydrogen fluoride to obtain (3,3,3-trifluoropropyl)benzene. However, since in the above-mentioned process, water is formed by the reaction, the activity of the catalyst is reduced during the reaction, and the recovery of once-used catalyst is difficult. Moreover, 3,3,3-trifluoropropyl ether as the starting material is synthesized by the reaction of hydrogen fluoride, formaldehyde (or its polymer) and vinylidene fluoride. Accordingly, 3,3,3-trifluoropropyl ether is expensive because of the high price of vinylidene fluoride and of the yield of synthesizing the ether as low as 50 to 60%.
It is an object of the present invention to provide a novel 3,3,3-trifluoropropyl derivative of naphthalene, 1-methylnaphthalene or 2-methylnaphthalene of the general formula ##STR2## wherein R.sup.1 and R.sup.2 respectively represent hydrogen atom or methyl group, with the proviso that R.sup.1 and R.sup.2 does not simultaneously represent methyl group; m and n respectively represent zero or 1, with the proviso that the sum of m and n is 1.
Another object is to provide a novel process for preparing the 3,3,3-trifluoropropyl derivative of naphthalene, 1-methylnaphthalene or 2-methylnaphthalene, which comprises bringing 3,3,3-trifluoropropene into reaction with naphthalene, 1-methylnaphthalene or 2-methylnaphthalene in the presence of an acid catalyst selected from the group consisting of hydrogen fluoride and boron trifluoride. A still further object is to provide a dielectric material comprising at least one of the 3,3,3-trifluoropropyl derivatives of naphthalene, 1-methylnaphthalene or 2-methylnaphthalene. A particular object is to provide 3,3,3-trifluoropropyl derivatives of naphthalene, 1-methylnaphthalene or 2-methylnaphthalene obtained by bringing 3,3,3-trifluoropropene into reaction with naphthalene, 1-methylnaphthalene or 2-methylnaphthalene in the presence of an acid catalyst, and separating the thus formed 3,3,3-trifluoropropyl derivative from the reaction mixture. Other objects will appear hereinafter in the description.